Author Topic: Starting a freshly built engine for the first time - CB750 (Read 8477 times)

andy750 · « **on:** August 16, 2006, 08:15:22 am »

I am now ready to start my freshly built CB750K2 cafe bike for the first time since I had the lower engine rebuilt (completely cleaned as well so no oil in there). I replaced the solenoid and coils and now have spark and so ready to fire it up. My mechanic (ex-Honda guy from the 70s) told me to use the electric start (with engine switch OFF) and build up oil pressure over the course of 15 mins with short bursts on the starter button. I tried this but the battery goes flat pretty quickly. Should I persevere with this technique (designed to get oil into the lower half) or does someone have an alternative way for firing up a rebuilt motor. and ensuring oil flow to lower half as quickly as possible. This engine rebuild was big $$$s so I dont want to ruin it by starting incorrectly!

Any help/advice much appreciated!
cheers
Andy in Boston

Short Round · « **Reply #1 on:** August 16, 2006, 09:38:42 am »

my advice would be to invest in a 12V jumper box and do as the ex-honda guy from the 70's told you to do. just undo your battery and hook the jumperbox up to the battery cables. this way your battery stays charged and your jumper box is ued for what it was built for. You will prob get about 10-15 bursts on a jumper box until its dead, maybe more, then just hook your battery back up and start it up.

Serge · « **Reply #2 on:** August 16, 2006, 09:45:02 am »

put bike on a side stand, take out a plug on the right side of the engine (the one which used to put an external oil pressure gauge) and pour some oil right in there. then do the crancking with ignition off. this will speed things up - serge

andy750 · « **Reply #3 on:** August 16, 2006, 09:59:06 am »

Thanks guys for the tips - both useful and I like the idea of the jumper box. Any particular reason why putting oil in #4 cylinder makes a difference?

cheers
Andy in Boston

hevykevy420 · « **Reply #4 on:** August 16, 2006, 10:03:45 am »

I don't think he means #4 spark plug.

this world is polluted enough!!!

I think there is a bolt somewhere on the block you can remove to put an oil pressure gauge in.

SOMEBODY ELSE KNOWS I"M SURE...

andy750 · « **Reply #5 on:** August 16, 2006, 10:24:59 am »

Oh right I see what he means - sorry for confusing the issue. Good idea and Ill try that. I have an ol pressure gauge there.

cheers
Andy

Bodi · « **Reply #6 on:** August 16, 2006, 10:58:15 am »

The engine should have been assembled with "assembly lube" on the bearings to manage friction until engine pressure builds up. It would be very poor practice to assemble it "dry", I don't know af any mechanic that would.
If it is dry, running the starter motor or even vigorous kicking (no plugs installed) will eventually fill the filter and galleries. Don't run the starter motor more than 30 seconds even with the plugs out, it is made for intermittent use only and will overheat quickly.
If it has the assembly lube applied, I would just start it and keep throttle and revs down until oil pressure shows up. It should only be a second or three to fill the filter and gallery.

Jonesy · « **Reply #7 on:** August 16, 2006, 11:49:12 am »

Did you prime the oil pump? If not, before you start spinning the starter, remove the oil pan and remove the cap holding the oil pressure relief valve. with no sparkplugs in the engine, crank it over a few times with the kicker and the oil tank full. Once oil starts flowing from the relief port, button everything back up on the bottom of the motor and remove the oil gallery plug (where your pressure gauge is. Hand kick it a few more times until you see oil appear. After replacing the gauge a few more hand kicks should have all the galleries filled. Also, remove one of the tappet covers and pour some oil in there. This will go to the sump and help prime the pump for the oil return.

I went through this on a motor I just redid. Cranked and cranked and cranked, nothing. Did what I just described and I had oil pressure in no time.

johnny-from-bel · « **Reply #8 on:** August 16, 2006, 12:35:28 pm »

Hey Andy,

The 750 engine is not as fragile as people think. Make shure there is oil in the system. Attach a manometer at the plug on the right side of the engine.
Kick it over a few times .
If ever you made a mistake and have the cam on 180 degrees or have the 'one touth off syndrom' you will hear the valves hitting the piston.
If that is ok, start the engine. You will probabely have to hook up a car battery as the standard battery is only good for a few tries. (No the car battery will not make the standard battery explode). Preasure buildup should be immediate. If not hit the kill switch and find out why. Usualy wrongly mounted oilfilter assembly.

As you are so much smarter than I, I am shure it will be OK.

Johnny-from-belgium.

O and after a minute or so put your finger in the oiltank an taste the oil. If it tastes like aluminium there is a blockage

Noel · « **Reply #9 on:** August 16, 2006, 01:00:05 pm »

Agree with Bodi. Unless a complete idiot rebuilt the engine, it will have been assembled with assembly lube, just like Honda did the first time around. IMO you should follow Honda's break-in suggestions, which don't incude anything that will drastically shorten the life of your starter motor.

dusterdude · « **Reply #10 on:** August 16, 2006, 01:51:11 pm »

hey johhny,does aluminum taste like chicken?

mrbreeze · « **Reply #11 on:** August 17, 2006, 01:21:56 am »

I would have to agree with Bodi that the inards should have an assembly lube and I would also hook up that oil gauge(If not to run permenent,just temp to acknowledge oil pressure).With the ignition disconnected,hit the starter in short bursts until you see pressure on the gauge (it shouldn't take long at all). Once you have a pressure reading,hook the ignition back up and get ready to hear it run and start the fun world of fine tuning!!!!!(Thats if you had it close enough to start with)

andy750 · « **Reply #12 on:** August 17, 2006, 05:34:42 am »

Thanks to all who have wrote for the very good advice as this is just what I was looking for - one thing Im not quite clear on - is how does turning over the starter motor (with ignition switched to off) actually help oil get into the lower case and fill up the galleries? how does this happen? Can someone explain this to me?

I understand that the starter switch turns the starter motor over via the solenoid....but how does this relate to oil pressure?

thanks for any info,
cheers
Andy

BobbyR · « **Reply #13 on:** August 17, 2006, 06:23:18 am »

Andy, your engine has an oil pump just like a car. It is not a splash system like a lawn mower. When you spin the engine with the starter the oil pump is turned. Removing the spark plugs will allow the engine to spin faster. The faster the engine spins the more oil is pumped and at a higher pressure. Remember only use the starter in short bursts of no more than 15 seconds.

andy750 · « **Reply #14 on:** August 17, 2006, 06:52:13 am »

Ah I see. Now that makes it clear -thanks Bobby. So I should be turning the starter over with spark plugs removed to build up pressure faster? I had been leaving them in and wondering why pressure wasnt moving (according to the gauge). Ill try without and keep to short bursts as recommended (once I get my jumpstart box from Sears).

many thanks
Andy

BobbyR · « **Reply #15 on:** August 17, 2006, 07:17:30 am »

Well you can use jumper cables atached to a car battery as long as you DO NOT HAVE the car running. If the car is NOT RUNNING your bike will only draw what it needs from the car's battery. With the car running, there can be a push from your car alternator which may cause some problems.

Bodi · « **Reply #16 on:** August 17, 2006, 08:43:36 am »

You'll see a huge difference with no spark plugs and no compression to crank against, the engine goes whirrrrrrr instead of plunka-plunka-plunka.
Turn your kill switch off to avoid damage to the ignition wires or coils with the plug wires hanging loose. With nowhere else to go, the ignition high voltage will try to jump through the cable insulation and the coil's internal insulation. If it does, it damages the insulation and makes misfires more likely even with the plugs in and connected. The coil system will produce extremely high voltages trying to dump its stored energy and it's likely to manage to spark somewhere!

andy750 · « **Reply #17 on:** August 17, 2006, 09:02:50 am »

Thanks Bodi that was a very good explanation and Im understanding a lot more now! Im looking forward to trying all these things when I get home. Is it necessary to remove all 4 plugs or are #1 and #4 removed enough to make a difference?

cheers
Andy

techy5025 · « **Reply #18 on:** August 17, 2006, 08:53:22 pm »

When I rebuilt my engine it was dry except for the bearings. I poured about
one quart of oil into the valve cover by removing one of the rocker arm adjustment
caps. It goes straight to the pan and will immerse the oil pump scavenge screen.
This will give the pump an immediate source of oil to build up pressure.

Obviously, you need the oil tank at the correct mark...actually at the top as it will
go down a little, oil filter in, etc. If the check valve in the oil pump is working
correctly, oil from the tank will not get to the engine until the pump is operating...
that's the way a "dry sump" engine works.

I actually started the bike.

Within two seconds the oil light went out indicating
pressure in the oil gallery. It ran rough as the carbs were not synced
exactly and timing was a little off, but the oil pressure came up quickly.

I think you will be OK as long as you don't race the engine until you are sure
you have pressure. You shouldn't do that until everything is adjusted anyway.

Edit: BTW...what I wrote above was just the way I attached the new engine
oil issue. After sleeping on it, I have decided it was probably a bit risky. Also, the
oil pump has two compartments...the bottom side grabs scavenge oil for the pan
and returns it to the oil tank. The top side gets oil from the tank and pressurizes
the oil gallery. Therefore I don't think filling the oil pan solved the problem of
getting oil to the gallery quickly.

Running just the starter should do it though.

Jim

HondaMan · « **Reply #19 on:** August 17, 2006, 09:02:33 pm »

Quote from: Littleitaly52 on August 16, 2006, 09:38:42 am

my advice would be to invest in a 12V jumper box and do as the ex-honda guy from the 70's told you to do. just undo your battery and hook the jumperbox up to the battery cables. this way your battery stays charged and your jumper box is ued for what it was built for. You will prob get about 10-15 bursts on a jumper box until its dead, maybe more, then just hook your battery back up and start it up.

When I rebuild these, I begin by kicking them over about 40-50 times in as much a continuous session as possible (it helps you lose weight!). Then, short bursts of 2-3 seconds of the starter until the oil light goes out. Then, when my leg recovers, I do it a 2nd time, then start it and run, as slowly as it will run, for about a minute.

The kicking/bursting routine will fill the oil filter and the lines, but will not force oil into the bearings the first time. After the second time, it will. The top end will not be oiled until the engine has run for a minute or so, due to air in the system at other points, so don't rev it until it's running pretty smoothly.

mrbreeze · « **Reply #20 on:** August 17, 2006, 10:36:19 pm »

You should (with any engine) make sure you have oil pressure before actually running it.What if you ran it and for some dumb ass reason,you got no oil pressure? Would it be better on your bearings if it turned over at a low amount of RPM"S or at 1000+ RPM's? And....when its running you have the extra burden of combustion in the mix. I like the idea of pulling the plugs for this oil pressure build up.Thats even less strain....think about it...this all makes perfect sense.

USCG_C130 · « **Reply #21 on:** July 04, 2013, 05:42:15 am »

Quote from: Jonesy on August 16, 2006, 11:49:12 am

Did you prime the oil pump? If not, before you start spinning the starter, remove the oil pan and remove the cap holding the oil pressure relief valve. with no sparkplugs in the engine, crank it over a few times with the kicker and the oil tank full. Once oil starts flowing from the relief port, button everything back up on the bottom of the motor and remove the oil gallery plug (where your pressure gauge is. Hand kick it a few more times until you see oil appear. After replacing the gauge a few more hand kicks should have all the galleries filled. Also, remove one of the tappet covers and pour some oil in there. This will go to the sump and help prime the pump for the oil return.

I went through this on a motor I just redid. Cranked and cranked and cranked, nothing. Did what I just described and I had oil pressure in no time.

i know i am reviving an older post but i found this very helpful, i finally started my bike for the first time ever since ive owned it and since i rebuilt the top end. i followed hondamans book and primed the oil pump beforehand. i used a big ol syringe type injector like we use at work and poured about 4= oz in the head and probably about 10oz in the gallery port and kicked and cranked it until oil started pouring from the gallery then put my direct reading gauge on and kicked a few more times until i saw about 10+ PSI and then put my plug back, and hit the started almost immediately my oil light went out and my gauge read 20PSI

i am running 20w-50 castrol and once its started i read about 70 PSI on the gauge

but i wanted to give a big thanks to the guys on this thread because i was nervous i know how critical oil pressure is and i didnt want to kill my motor on day 1 this made life sooo easy!

MRieck · « **Reply #22 on:** July 04, 2013, 07:13:34 am »

Quote from: USCG_C130 on July 04, 2013, 05:42:15 am

Quote from: Jonesy on August 16, 2006, 11:49:12 am
Did you prime the oil pump? If not, before you start spinning the starter, remove the oil pan and remove the cap holding the oil pressure relief valve. with no sparkplugs in the engine, crank it over a few times with the kicker and the oil tank full. Once oil starts flowing from the relief port, button everything back up on the bottom of the motor and remove the oil gallery plug (where your pressure gauge is. Hand kick it a few more times until you see oil appear. After replacing the gauge a few more hand kicks should have all the galleries filled. Also, remove one of the tappet covers and pour some oil in there. This will go to the sump and help prime the pump for the oil return.

I went through this on a motor I just redid. Cranked and cranked and cranked, nothing. Did what I just described and I had oil pressure in no time.

i know i am reviving an older post but i found this very helpful, i finally started my bike for the first time ever since ive owned it and since i rebuilt the top end. i followed hondamans book and primed the oil pump beforehand. i used a big ol syringe type injector like we use at work and poured about 4= oz in the head and probably about 10oz in the gallery port and kicked and cranked it until oil started pouring from the gallery then put my direct reading gauge on and kicked a few more times until i saw about 10+ PSI and then put my plug back, and hit the started almost immediately my oil light went out and my gauge read 20PSI

i am running 20w-50 castrol and once its started i read about 70 PSI on the gauge

but i wanted to give a big thanks to the guys on this thread because i was nervous i know how critical oil pressure is and i didnt want to kill my motor on day 1 this made life sooo easy!

That's OK....Andy is still trying to build oil pressure in that engine.

grumpy · « **Reply #23 on:** July 04, 2013, 07:33:01 am »

how 'bout this?

pull the plugs
put it on the centerstand
slide the wife's treadmill under the rear wheel
put the bike in gear
turn on the treadmill...

Bootlegger56 · « **Reply #24 on:** July 04, 2013, 09:14:41 am »

I'm all in on the treadmill idea!!!

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Author Topic: Starting a freshly built engine for the first time - CB750 (Read 8477 times)

johnny-from-bel